1. Field of the Invention
In recent years many petrochemical companies have become increasingly interested in the utilization of hydrocarbon by-products from ethylene plants because of the increased availability and lower costs of these hydrocarbons as compared with their polymer grade counterparts. It has now been discovered that elastomers synthesized from C.sub.5 -hydrocarbons, when used in combination with certain natural or synthetic tackifiers, are particularly suited for use as pressure-sensitive adhesives. This is very encouraging in view of existing natural resin shortages and the fact that the adhesives industry is placing increasing emphasis on adhesives containing tackifiers of synthetic origin. The adhesives as defined herein have superior characteristics such as tack, peel strength, creep, tensile strength, plasticity, and stability to oxygen and aging.
2. Description of the Prior Art
The use of an isoprene-piperylene copolymer in an adhesive composition is disclosed in U.S. Pat. No. 3,919,160 issued Nov. 11, 1976, to Lakshmanan for Adhesive Composition, which teaches an adhesive composition consisting of a styrene-butadiene block copolymer, a styrene-isoprene block copolymer, an isoprene-piperylene copolymer (tackifier) and a solvent. The adhesive composition fails, however, to appreciate the particular tackifier/elastomer and solvent combination in the adhesive composition disclosed herein which consists essentially of an isoprene-piperylene elastomer, a synthetic tackifier or a natural tackifier and solvent. Additionally, the adhesive composition disclosed in this reference is not used in context of a pressure sensitive adhesive (i.e. for masking tape, scotch tape, surgical tape, labels, etc.). Instead it is described as suitable for use in bonding wood, plastic, metal, a cellulosic material, such as paper, and glass, etc., to itself or to another member of such group.